1. Field of the Invention
This invention relates to a rust removing agent for a stainless steel surface, which removes rust and invisible rust formed on a stainless steel surface.
2. Description of the Prior Art
Stainless steel has found utility in numerous applications. However, depending on atmospheric and other various environmental conditions, rust or invisible rust sometimes forms on the surfaces of cast or shaped products of stainless steel.
Such rust and invisible rust degrade the smoothness of a stainless steel surface. Particularly, in the case of a building material for interior use or a finishing material made of stainless steel, the rust and invisible rust impair the good appearance of the material. In the case of ordinary structural members of stainless steel which are joined by welding, the rust and invisible rust often degrades the strength of union.
Further, when the rust once formed is left standing, the corrosion originating in the rust advances and grows into pitting corrosion or goes to impair the strength of the stainless steel partially or wholly, possibly causing various troubles. Various methods have been proposed and applied for the removal of such rust. A method which attains removal of rust from a stainless steel surface by immersing the stainless steel article in an acid wash bath formed by combining such strong acids as sulfuric acid, hydrochloric acid, hydrofluoric acid, and nitric acid, a method which effects removal of rust from a stainless steel surface by preparing a viscous pasty coating agent by mixing an acid wash with a viscosity enhancer such as acid clay or carboxymethyl cellulose (C.M.C.) or with a film-forming agent such as vinyl acetate, an alginate, or gelatin, applying the coating agent to the rusted stainless steel surface, allowing the coating agent to react with the rust on the surface, and thereafter washing off or peeling the applied layer of the coating agent, and a method which accomplishes removal of rust from a stainless steel surface by subjecting the stainless steel article to an electrolytic treatment in an electrolytic solution thereby inducing generation of hydrogen from the surface may be cited, for example.
Among the methods described above, the method involving the immersion of the stainless steel article in the acid wash bath and the method involving the application of the acid wash in the form of a viscous pasty coating agent to the surface both use an acid wash incorporating strong acids therein and, therefore, require special care in the handling of the hazardous chemical and to the selection of equipment suitable for use in carrying out the treatment.
Further, the aforementioned acid wash acts not only the rust but also on the stainless steel itself and eventually coarsens the surface under treatment. In some cases the stainless steel surface which has been treated with the acid wash will require an extra passivating treatment for imparting corrosion resistance to the surface.
The method involving the electropolishing treatment of a stainless steel surface with an electropolishing bath requires a long time for the treatment and necessitates use of a high capacity power source and electrolytic device because the stainless steel article under treatment serves as one of the electrodes for the electrolysis. This method, therefore, is not suitable for the removal of locally formed rust and inapplicable to the treatment of stainless steel used in structural members joined by welding.
This invention was accomplished in the light of the problems of prior art described above and has as its object to provide a rust removing agent which is capable of quickly and efficiently removing rust formed on a stainless steel surface.
Another object of this invention is to provide a rust removing agent which is capable of passivating a stainless steel surface without causing corrosion of the surface or necessitating any special treatment.